Tea Safety – What are the Key Areas of Food Safety in Tea Manufacturing - II

Export Compliances of Tea

Made Tea, processed leaves of Camellia sinensis, has been imported into Europe for over 200 years with few, if any, reported safety concerns and has consequently been deemed to be ‘low’ risk in terms of food safety, which is an agricultural product that is predominantly grown, harvested and processed in developing countries. Made tea is sold on the world market either by Public Auction or Private Treaty (either directly by the producer or via a broker or trader). 

Thus it is generally impractical for the buyers to exert any direct control over the tea manufacturing process or to directly control food safety issues addressed during the process which is controlled in EU through Regulation (EC) No 852/2004 concerning the hygiene of foodstuffs places an obligation on food business operators to ensure that all stages of production, processing and distribution of food under their control satisfies the relevant hygiene requirements laid down in the Regulation. It requires all food business operators put in place, implement and maintain a permanent procedure or procedures based on Hazard Analysis and Critical Control Point (HACCP) principles which will also apply to tea processors carrying out any stage of production, processing and distribution of food after primary production and associated operations. The same requirements are requested in other food safety standards and buyers in different regions, thus common understanding is that, procedures based on the HACCP principles should not only apply to primary production of tea but food hazards present at all the steps of primary production and associated operations should be identified and adequately controlled to ensure the achievement of the objectives of food safety.

 

Here is the rest of the food safety issues considered from last article.

Physical Contamination

Foreign matter or physical contaminants can be extraneous material naturally associated with tea, e.g. parts of other plants growing nearby, or foreign material introduced during the process, such as stones, glass, metal, scale, insect fragments, jewelry, packaging materials etc. Thus teas received by packers can contain a variety of extraneous matters, but there are various steps in the manufacturing process designed to remove foreign matter, where the quantity present is very low and its nature presents little food safety risk. The considered low risk is further reduced, because stringent cleaning processes employed by the packer and the manner in which the consumer prepares the beverage. 

However, tea is mostly contaminated with iron particles due to various machinates use as well as their direct contact with the product. Thus iron removal is considered as stage wise process, where magnets are usually located in dryer mouth, winnower belt, colour sorter to catch iron particles in various stages of the process.    

Microbiological Contamination

There are no reported microbiological food safety hazards relating to made tea. However, there are risks in the contamination at the processing stages due to environmental factors or personnel hygiene which is arrested at the drying process. However, tea contains a natural level of micro-organisms but tea has low water activity, where it presents negligible hazard providing that tea is kept dry.

The European Union’s Scientific Committee on Food reviewed the micro-biological risks associated with tea in 1997 and concluded that: Tea has a long history of safe use and the Committee is unaware of any safety problems related to moisture in tea, which may be attributed to its low moisture content (i.e. low water activity) and the high content of anti-microbial substances. Moisture levels up to 10% seem to give an acceptable safety margin for the storage of tea.

But in a hazard assessment, you need to consider following microbes as potential biological hazards and then you can justify your decision of they have low risk to cause food safety contaminations at initial stages of processing, but you need to have appropriate preventive measures established before you claim the low risk in your production process.     

Aflatoxins

Aflatoxins are a group of mycotoxins produced by Aspergillus flavus and Aspergillus parasiticus. These may grow in plant leaves, nuts, dried fruit and infect stored cereal grains where they produce the aflatoxins. When such toxins are formed they do not go away. They are heat stable, and thus stay in the food along the food chain, unaffected by heat treatments such as pasteurization. When a cow eats a feed contaminated with aflatoxin B1, the activity of the cow changes the aflatoxin B1 to aflatoxin M1, which ends up in the milk (Johnsson, 2006).

The toxicity of aflatoxin is mainly due to its carcinogenicity. This is because aflatoxins are genotoxic, meaning it affects the genetic material. Genotoxins have a direct dose-response relationship, so they do not have a threshold dose to exceed before they have effect. Thus, there is no tolerable daily intake (TDI) for aflatoxins, which are to be kept at a level as low as possible. Though, maximum levels are set in the European Union, for example 0.05 μg/kg of milk for aflatoxin M1.

Mycotoxins

Mycotoxins are produced by mold, and there is a range of different compounds originating from different types of mould among the Deuteromycetes. The Mycotoxins are secondary metabolites, toxic in low concentrations in vertebrates.

Mycotoxins in the product can only be prevented at the source where the mould infection occurs, since the toxins are impossible to remove. In the case of made tea, control measures could be taken at the production and handling.

Except for the opinions, there are no proper examples available to prove aflatoxin contamination in made tea.   Thus, there is a very minimal risk for getting the aflatoxins into the made tea. Since aflatoxins have a cumulative negative effect in humans they shall be considered as hazards in the HACCP plan of the ISO 22000 FSMS.

Salmonella spp.

Salmonella spp. is a gram-negative, facultative anaerobic organism, which does not form spores. Growth occurs at 5 – 47°C, and the organism is heat sensitive. It is a zoonotic organism, which may be found in different animals’ guts.

Because Salmonella may be found in animals, it has a good chance of contaminating foodstuff of animal origin, like meat, milk and egg. For an example, Sweden and Finland there is zero-tolerance regarding Salmonella infection among domestic animals, which lowers the risk of human infection. Good handling and heat treatment of the food is necessary to decrease the risk.

Salmonella may cause either enteritis or a systemic infection. The gastrointestinal infection has symptoms as milk fever, vomiting and diarrhoea lasting for a few days up to more than a week. The infectious dose is in the order of 106 cells, but in some cases it has been much lower than that. The systemic infection is caused by invasive, host-adapted serotypes. The bacteria then spread in the body and causes fever, headache and diarrhoea. Salmonella infection may be fatal.

The tea leaves are plucked and heaped on the floor or in the field and transported to the factory with high risk of contamination form humans due to handling. The raw material further directly handled by many operators during withering, rolling, fermentation, sifting and packing, which increase the risk of Salmonella infection. Hence, there is a risk for Salmonella contamination in the product. Luckily the organism’s heat sensitivity makes it possible to eliminate with LTHT treatment. The severity of the disease in combination with the risk makes Salmonella a hazard to target in the HACCP plan.

Escherichia coli 

Escherichia coli are in the family Enterobacteriaceae, gram negative, rod shaped, non-spore forming, and motile or non-motile. They can grow under aerobic and anaerobic conditions where grow best at 37⁰C. Therefore, it is easy to eradicate by simple boiling or basic sterilization. 

E. coli O157:H7 is a well-studied strain of the bacterium E. coli, which produces Shiga-like toxins, causing severe illness. E. coli is transmitted to humans primarily through consumption of contaminated foods, faecal contamination of water and other foods. Infectious dose of E. Coli is 106 - 108 logs of organisms.

The tea leaves are plucked and heaped on the floor or in the field and transported to the factory with high risk of contamination or cross contamination from humans due to handling. The raw material further directly handled by many operators during withering, rolling, fermentation, sifting and packing, which increase the risk of E. coli infection. Hence, there is a risk for E. coli contamination in the product due to poor personal hygiene and improper cleaning of utensils. Luckily the organism’s heat sensitivity makes it possible to eliminate with LTHT treatment. The severity of the disease in combination with the risk makes E. coli a hazard to target in the HACCP plan.

Staphylococcus aureus

Staphylococcus aureus is a facultative anaerobic organism, which does not form spores. Growth occurs at 7 – 45°C with optimum growth at 37°C, and the organism is heat sensitive. The presence of Staphylococcus aureus is of concern in products that are fermented. Staphylococcus aureus can multiply to high numbers during fermentation if the product is not rapidly fermented (e.g., the starter culture is not active) and cause a toxin to be produced that can cause illness to consumers.

The bacteria are common in the environment and are often found on skin, nose, mouth or boils and cuts of people. The product may generally become contaminated with Staphylococcus aureus from the raw materials or from human contact.

Generally, it takes high numbers and growth of Staphylococcus aureus to cause a hazard with a medium dose. The symptoms of Staphylococcus aureus food poisoning are nausea, vomiting, stomach cramps, prostration, diarrhoea and last for 6 to 24 hours.

Proper cooking, fermentation, cooling, storage and personal hygiene of food handlers can prevent growth while minimizing cross contamination of Staphylococcus aureus and more importantly, the production of their toxins. However, cooking will not destroy toxins once they are formed in food.

The tea leaves are plucked and heaped on the bare floor or in the field and transported to the factory with high risk of contamination form humans due to handling. The raw material further directly handled by many operators during withering, rolling, fermentation, sifting and packing, which increase the risk of Staphylococcus aureus contamination. Further, the intermediate product is fermented for minimum 2.5 hours and may be as long as 6 hours in some specific tea grades. The severity of the disease in combination with the risk makes Staphylococcus aureus a hazard to target in the HACCP plan.

The Radioactivity of Japanese Tea 

Following the March 11th earthquake and subsequent problems at the Fukushima Daiichi nuclear power plant, reports surfaced of radiation in the Japanese food supply. After immediate concern for the Japanese people, many people began to wonder: how will this affect tea? Because tea is a $1.3 billion (2009) industry for Japan and it is beyond the tea leaves used for brewing a fresh cup, green tea is also used in flavouring for many Japanese products. Ground dried tea leaves are processed into seasonings for foods like cookies and ice cream, leaving the potential for further radiation exposure in the food supply.

The disaster at the Fukushima Daiichi nuclear power plant led to the release of radioactive isotopes into the air (predominantly cesium-137 and iodine-131, and some cesium-134), where exact amount of radioactivity released into the air is unknown, but it is estimated to be 770,000 trillion Becquerels (a unit of measure - Bq) of radioactive particles. This formed a large plume that generally followed the major wind patterns and moved most of the radiation east, over the Pacific Ocean while, some radioactive contamination moved into other areas of Japan since atmospheric events like rain, low pressure systems, wind changes and the altitude of the plume affect movement. Considering the radioactive chemicals, Cesium-137 is more of a long-term concern than iodine-131, as the Cesium isotope’s half-life (the length of time required for the amount of the substance to reduce by half) is about 30 years vs. iodine-131’s half-life of 8 days. There is a short-term risk of thyroid damage if radioactive iodine in food is absorbed into the body and accumulates.

The World Health Organization (WHO) and the Food and Agricultural Organization (FAO) jointly set standards for radiation in food products, through Codex General Standard for Contaminants and Toxins in Food and Feed, which contain Codex Guideline Levels, which is maximum of 1000 Bq/kg for cesium-137 and 100 Bq/kg for iodine-131. In comparison, the U.S. Food and Drug Administration has a border intervention level of 1200 Bq/kg of Cesium for imported goods. Another variable is how much of the radioactive material actually enters the liquid when the leaves are steeped. The tests the Japanese Tea Exporters’ Association conducted (10g leaves/430 ml water/90C/60 seconds) with leaves sampled in May found that steeped tea from Shizuoka is safe to drink. There is little conclusive information on how much radioactive material could get into the tea liquid, since there are so many factors involved in both processing and brewing tea, and some teas are steeped multiple times; estimates have ranged anywhere from 2% to 16%.